Demonstrate conversion from standard Yesod to yesod-pure

fib.hs

{-# LANGUAGE MultiParamTypeClasses #-}
{-# LANGUAGE OverloadedStrings     #-}
{-# LANGUAGE QuasiQuotes           #-}
{-# LANGUAGE TemplateHaskell       #-}
{-# LANGUAGE TypeFamilies          #-}
import           Yesod

data App = App

mkYesod "App" [parseRoutes|
/ HomeR GET
/fib/#Int FibR GET
|]

instance Yesod App

getHomeR :: Handler RepHtml
getHomeR = defaultLayout $ do
    setTitle "Hello World!"
    toWidget [whamlet|
<p>Hello World
<a href=@{FibR 5}>Fifth fib
|]
    toWidget [lucius|p { color: red }|]

getFibR :: Int -> Handler RepHtml
getFibR i = defaultLayout $ do
    setTitle "Fibs"
    [whamlet|
<p>Fib for #{i}: #{fib i}
<a href=@{FibR $ i + 1}>Next fib
|]

fib :: Int -> Int
fib i = fibs !! i

fibs :: [Int]
fibs = 0 : 1 : zipWith (+) fibs (tail fibs)

main :: IO ()
main = warpDebug 3000 App